1. Field of the Disclosure
The disclosure relates generally to drilling systems. More particularly, the disclosure relates to drilling fluid circulation and sampling systems for drilling operations.
2. Background of the Technology
To drill a borehole in the earth for the recovery of hydrocarbons (e.g., oil and gas), an earth-boring drill bit is mounted on the lower end of a tubular drill string and is rotated. With weight applied to the drill string, also referred to as weight-on-bit (WOB), the rotating drill bit engages the earthen formation and proceeds to form a borehole along a predetermined path toward a target zone. While the bit is rotated, drilling fluid is pumped from the surface through the drill string and directed out of nozzles in the face of the drill bit into the bottom of the borehole. The drilling fluid exiting the bit is forced from the bottom of the borehole to the surface through the annulus between the drill string and the borehole sidewall.
The drilling fluid, also referred to as drilling mud, performs several functions—maintains a desired pressure within the borehole, cools and lubricates the drill bit, carries rock cuttings to the surface, maintains borehole stability, and transmits hydraulic energy to downhole tools. For example, managing the pressure in the well is important to inhibit the influx of formation fluids into the wellbore, while ensuring excessive wellbore pressure does not fracture the formation and lead to significant drilling fluid loss into the formation. The drilling fluid returning to the surface via the annulus is processed and reconditioned to remove rock cuttings, sand and other solids, as well as to ensure proper mud weight and density, pH, etc. After such processing and reconditioning, the drilling fluid is temporarily stored in mud tanks at the surface, and then pumped back down the drillstring. In this manner, the drilling fluid is continuously recirculated through the drilling system.
As the drilling fluid is circulated through the drilling system, samples of the drilling fluid returning to the surface are continuously taken to identify species of interest (liquids and gases) in the drilling fluid. Typically, the species of interest in the returning drilling fluid to be identified and monitored include hydrocarbons (e.g., methane, ethane, propane, i-butane, n-butane, i-pentane, n-pentane, n-hexane, ethane, propene, etc.), carbon dioxide, hydrogen, helium, sulfur dioxide, benzene, and hydrogen sulfide. In particular, the drilling fluid samples are heated to volatize or vaporize any liquid species of interest in the drilling fluid. Typically, electric heaters are employed to heat the drilling fluid samples. Once volatized and separated from the drilling fluid, the species of interest are transported to analytical equipment for further processing and analysis. This process of removing species of interest from drilling fluid for analytical purposes is commonly referred to as “degassing” or “extracting,” with the resulting gaseous samples being called “representative sample gas” as it is generally representative of the species of interest in the returned drilling fluid stream at that particular time. Once the species of interest are removed, the heated drilling fluid is returned to the drilling process. However, the thermal energy in the heated samples of drilling fluid may detrimentally impact the equipment (e.g., pumps) used to transport the drilling fluid back to the drilling process. Moreover, the hot samples of drilling fluid present a potential safety hazard to personnel positioned near the drilling fluid sample return line.